<template>
  <el-color-picker class="theme-picker" popper-class="theme-picker-dropdown" v-model="theme" :size="size">

  </el-color-picker>
</template>

<script>
const version = require('element-ui/package.json').version
const ORIGINAL_THEME = '#409EFF'

export default {
  name: "ThemePicker",
  props:{
    // 初始化主题,可由外部传入
    default:{
      type: String,
      default: null
    },
    // 初始化主题,可由外部传入
    size:{
      type:String,
      default: 'small'
    }
  },
  data(){
    return{
      // content of theme-chalk css
      chalk: '',
      theme: ORIGINAL_THEME,
      // 是否弹出换肤成功消息
      showSuccess: true
    }
  },
  mounted(){
    if (this.default != null){
      this.theme = this.default
      this.$emit('onThemeChange',this.theme)
      this.showSuccess = false
    }
  },
  methods: {
    updateStyle(style, oldCluster, newCluster) {
      let newStyle = style
      oldCluster.forEach((color, index) => {
        newStyle = newStyle.replace(new RegExp(color, 'ig'), newCluster[index])
      })
      return newStyle
    },

    getCSSString(url, callback, variable) {
      const xhr = new XMLHttpRequest()
      xhr.onreadystatechange = () => {
        if (xhr.readyState === 4 && xhr.status === 200) {
          this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, '')
          callback()
        }
      }
      xhr.open('GET', url)
      xhr.send()
    },

    getThemeCluster(theme) {
      const tintColor = (color, tint) => {
        let red = parseInt(color.slice(0, 2), 16)
        let green = parseInt(color.slice(2, 4), 16)
        let blue = parseInt(color.slice(4, 6), 16)

        if (tint === 0) { // when primary color is in its rgb space
          return [red, green, blue].join(',')
        } else {
          red += Math.round(tint * (255 - red))
          green += Math.round(tint * (255 - green))
          blue += Math.round(tint * (255 - blue))

          red = red.toString(16)
          green = green.toString(16)
          blue = blue.toString(16)

          return `#${red}${green}${blue}`
        }
      }

      const shadeColor = (color, shade) => {
        let red = parseInt(color.slice(0, 2), 16)
        let green = parseInt(color.slice(2, 4), 16)
        let blue = parseInt(color.slice(4, 6), 16)

        red = Math.round((1 - shade) * red)
        green = Math.round((1 - shade) * green)
        blue = Math.round((1 - shade) * blue)

        red = red.toString(16)
        green = green.toString(16)
        blue = blue.toString(16)

        return `#${red}${green}${blue}`
      }

      const clusters = [theme]
      for (let i = 0; i <= 9; i++) {
        clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
      }
      clusters.push(shadeColor(theme, 0.1))
      return clusters
    }
  },
  watch: {
    theme(val,oldVal) {
      if(typeof val !== 'string') {
        return;
      }
      // 替换 CSS 样式,修改主题颜色
      const themCluster = this.getThemeCluster(val.replace('#',''))
      const originalCluster = this.getThemeCluster(oldVal.replace('#',''))
      console.log('新的主题: ',themCluster, '旧的主题: ' ,originalCluster)
      const getHandler = (variable,id) => {
        return () => {
          const originalCluster = this.getThemeCluster(ORIGINAL_THEME.replace('#',''))
          const newStyle = this.updateStyle(this[variable], originalCluster, themCluster)
          let styleTag = document.getElementById(id)
          if (!styleTag) {
            styleTag = document.createElement('style')
            styleTag.setAttribute('id', id)
            document.head.appendChild(styleTag)
          }
          styleTag.innerText = newStyle
        }
      }
      const chalkHandler = getHandler('chalk','chalk-style')
      if (!this.chalk) {
        const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
        this.getCSSString(url, chalkHandler, 'chalk')
      }
      else {
        chalkHandler()
      }
      const styles = [].slice.call(document.querySelectorAll('style')).filter(style => {
        const  text = style.innerText
        return new RegExp(oldVal, 'i').test(text) && !/Chalk Variables/.test(text)
      })
      styles.forEach(style => {
        const {innerText} = style
        if (typeof  innerText !== 'string') {
          return;
        }
        style.innerText = this.updateStyle(innerText, originalCluster, themCluster)
      })
      this.$emit('onThemeChange',val)
      if (this.showSuccess) {
        this.$message({message:'换肤成功',type:'success'})
      }
      else {
        this.showSuccess = true
      }
    }
  }
}
</script>

<style scoped>
.theme-picker .el-color-picker__trigger {
  vertical-align: middle;
}

.theme-picker-dropdown .el-color-dropdown__link-btn {
  display: none;
}
</style>
